Originating, for practical purposes, with the development of inexpensive, low-loss optical fiber waveguides, optical communications technology has become well-established especially in long-distance, "inter-exchange" communications. More recently, interest has been growing in bringing optical signals closer to their ultimate destination such as, e.g., individual subscriber telephones, facsimile terminals, and data-processing equipment. In a primary field of application, namely the so-called local loop, it is desired to bring single-mode optical signals to the subscriber. And, in so-called local-area networks (LAN), multi-mode signals are being used in communications over relatively short distances such as, e.g., internal to a building or plant.
While, in long-distance communications, the cost of the fiber transmission medium is determinative of commercial feasibility, the total cost of local applications is dominated by the cost of components such as, e.g., optical sources, detectors, connectors, and couplers. Thus, the commercial feasibility of optical communications in local situations depends largely on the availability of low-cost optical components and on inexpensive ways of connecting components to optical fibers. Considered as particularly desirable in this respect are inexpensive means for connecting optical fibers and other optical components to substrate-supported waveguides, proper alignment of a component relative to the waveguide being a primary concern in such connections. For earlier work in this field see, e.g.,
L. P. Boivin, "Thin-Film Laser-to-Fiber Coupler", Applied Optics, Vol. 13 (1974), pp. 391-395;
H. P. Hsu et al., "Optical Fibers and Channel Waveguides", Electronics Letters, Vol. 12 (1976), pp. 404-405; and
J. T. Boyd et al., "Optical Coupling from Fibers to Channel Waveguides Formed on Silicon", Applied Optics, Vol. 17 (1978), pp. 895-898.